The present invention relates to a gas flow type angular velocity sensor which is capable of sensing an angular velocity acting on the sensor's body.
Generally, a gas flow type angular velocity sensor is constructed in such a way that a gas is forced into a gas path 10 in a closed casing 8 through a nozzle hole 9 to flow therealong toward a flow sensor 11 consisting of a pair of heat wires 111, 112 as shown in FIG. 9. When an angular velocity ".omega." is applied on the sensor body, the gas flow is deflected to one side by a value of deflection ".epsilon." from an axis 0--0 as shown in FIG. 10. This produces a difference between temperature sensitive outputs of two heat wires 111, 112 made of tungsten or a like material having a high temperature resistance coefficient. The difference is picked up for determining therefrom a direction and a magnitude of the angular velocity ".omega." acting on the sensor body.
The heat wires 111, 112 are arranged opposite to each other at both sides of the centerline 0--0 of the nozzle hole 9 and the gas path 10. When no lateral angular velocity ".omega." acts on the sensor body, gas injected through the nozzle hole 9 flows straight along the line 0--0 and evenly over the wires 111 and 112.
Consequently, it becomes possible to measure a value of change in moving direction of a moving body when the latter is equipped with such a gas flow type angular velocity sensor.
In FIG. 9, at least two flow-rectifying holes 14 are arranged at opposite sides along the axis of the nozzle hole 9 so as to rectify a flow of gas injected into a gas path 10 through a nozzle hole 9.
Since its detecting accuracy depends upon the accuracy of finishing of its components, the detector must have a precisely formed nozzle hole 9 and gas path 10 so that gas forced into the gas path 10 through the nozzle hole 9 may flow straight along a center line 0--0 when no lateral angular velocity ".omega." acts on the sensor body.
In a conventional gas flow type angular velocity sensor the nozzle hole 9 and gas path 10 are formed by cutting aluminum tubes.
However, said method for making the nozzle hole 9 and the gas path 10 requires a high technique of precision working.
In the gas flow type angular velocity sensor, since the finer the heat wires 111 and 112 are; the higher the sensitivity of the sensor 11 is, i.e. less displacement of the gas flow can be detected, the heat wires 111 and 112 are usually formed about 5 .mu.m in diameter.
Usually, each of the heat wires 111 and 112 is formed as a fine filament and then stretched between two supporting electrodes 17 mounted on a base plate 16 as shown in FIG. 11.
As shown in FIG. 9, the conventional gas flow type angular velocity sensor is provided at one end of its casing 8 with a diaphragm pump 12 whereby gas filled in the closed casing 8 is circulated in such a way that it flows through a path 13 and then through a nozzle hole 9 enters into a gas path 10 to create therein a laminar flow.
Furthermore, in the conventional gas flow type angular velocity sensor shown in FIG. 9, a circuit board 15, whereon an amplifier circuit and all portions of the resistance bridge circuit except the paired heat wires are attached to one end of the casing 8 as separated from sensor body. In this case soldered lead-wire connections must be made between the paired heat wires in the sensor body and corresponding terminals on the circuit board 15. This causes a contact resistance at the connections and thermoelectromotive force due to dissimilar metals' junction and correspondingly the accuracy of angular velocity measurement drops.